fn assemble_candidates_from_predicates<'cx, 'tcx>(
    selcx: &mut SelectionContext<'cx, 'tcx>,
    obligation: &ProjectionTermObligation<'tcx>,
    candidate_set: &mut ProjectionCandidateSet<'tcx>,
    ctor: fn(_: PolyProjectionPredicate<'tcx>) -> ProjectionCandidate<'tcx>,
    env_predicates: impl Iterator<Item = Clause<'tcx>>,
    potentially_unnormalized_candidates: bool,
)